Pressurised deaerators eliminate corrosive gases caused by oxygen. Adding to the problem is carbon dioxide which brings the pH down further resulting in more acidic water and increasing the corrosion rate further. Elimination is by chemical and physical methods, however sometimes there are plants that will need to reduce the amount of chemicals used due to special applications or standards and this is where a pressurised deaerator comes into its own.
The head section of the deaerator takes the water and breaks it down into small droplets surrounded by steam. This results in a high surface area to mass ratio and allows rapid heat transfer from the steam to the water, which then attains steam saturation temperature. The dissolved gases are released and carried with the excess steam to be vented to the atmosphere from the deaerator head. The deaerated water then falls to the storage section of the vessel and a blanket of steam is maintained above the stored water to ensure that gases are not then reabsorbed.
A modulating control valve maintains the water level to give stable operating conditions and a second control valve regulates the steam supply to raise the water to the temperature required. Steam is injected by means of a diffuser to give a good distribution of steam within the deaerator head. The steam also transports gases to the air vents to form a blanket of steam above the deaerated water in the vessel.
Flash Condensing Deaerator Head
Flash condensing consists of several segments, the mixing head with the mounting flange, stainless steel immersion tube with a plate top flange and two gaskets. The mixing head mixes incoming flows of condensate from the system, flash steam, cold water make-up feed and recirculation feed. Each inlet connection has an internal sparge which sprays the flow in various directions within the head. Gases are then emitted into the atmosphere.